Field of the Invention
The field of the present invention relates to sound reproduction and, more specifically, to speaker configurations and enclosures.
Background of the Related Art
Many sound reproduction systems include a subwoofer loudspeaker for reproducing very low frequency audio signals. Subwoofers may find use in a variety of settings including home audio systems, automobile sound systems, cinema audio systems, home theater systems, and live performance sound systems, among others.
Despite their popularity, conventional subwoofers suffer from a number of potential drawbacks or disadvantages. For example, subwoofer speakers can take up an inordinate amount of space. The size and shape of subwoofer speaker cabinets can be difficult to place in listening areas of limited size or with structural limitations, such as in automobiles and in many home environments. A common subwoofer cabinet is generally cubic in shape, and can be difficult to place in speaker cabinets or within the confines of an automobile, or in other limited spaces.
It is commonly understood that a subwoofer that for optimal sound reproduction of very low frequencies, a subwoofer driver should be relatively large in diameter, as compared with other drivers (for high- and mid-range frequencies for instance), which in turn means that the driver will generally have a relatively deep cone. It is also typical to construct a subwoofer speaker enclosure with a large cavity to allow the driver adequate ability to move an appropriate volume of air. Together these considerations often lead to subwoofer cabinets of bulky design that do not fit easily in limited spaces.
Another problem with subwoofer speakers is that they can create undesirable vibrations of nearby objects, in part because of the relatively large and forceful excursions made by the subwoofer driver as it reproduces very low frequency sounds. This phenomenon may not be as noticeable with standalone subwoofer speaker cabinets, but manifests more commonly in subwoofers that are designed as integral components of a larger structure, such as recessed subwoofers that are built into a wall of a home or building, or subwoofer loudspeakers that are integrated into an automobile. Because subwoofers in these settings are directly or indirectly physically attached to a building structure or automobile frame, their deep vibrations can be carried through the structure or framing to other items attached thereto or to adjoining rooms in a house or structure, causing noticeable rattling or even forcing objects to move or causing damage. The vibrations from the very lower frequencies reproduced by a subwoofer can be easily transmitted through a house or building while the higher frequencies are dampened, causing deep vibrations that can disturb other occupants or neighbors.
Standalone subwoofer speaker cabinets can also suffer from similar problems. Standalone speaker cabinets are sometimes placed in discreet or unobtrusive locations such as in room corners, low cabinets, and the like, but due to their excessive vibrations they have limited ability to serve other functions. For example, objects placed on standalone speaker enclosures may rattle noticeably, gradually slide across the surface, or fall off, causing annoying noise or damaging the objects.
Some subwoofer loudspeakers include two (or more) drivers, which may be done in order to increase sound output or, in some designs, to reduce vibrations of the cabinet or enclosure. When two drivers are oriented so that they directly face one another, the motion of the drive units is symmetric and the opposing movements of the two drivers may cancel out, reducing the vibration of the cabinet or enclosure. One drawback with this type of design, however, is that the speaker cabinet or enclosure must be deep enough to contain two face-to-face drivers, which can lead to even larger, bulkier cabinets or enclosures that are harder to place in limited spaces. Thus, consumers and sound system designers are often left with the choice of tolerating some level of cabinet/enclosure vibration, or else having to find placement for a large, bulky subwoofer loudspeaker.
It would be advantageous to provide a subwoofer or similar speaker design that has a narrower profile, so that it can be utilized in smaller or narrower spaces. It would further be advantageous to provide a subwoofer with reduced vibration while maintaining a high level of sound output and fidelity. It would further be advantageous to provide a subwoofer that is well suited for use as a recessed speaker in a home or building, or in the confines of an automobile.